In DE 35 46 454 C2, the prior art has disclosed a dual-clutch transmission in which the output sides of two axially immediately consecutive starting and gear clutches can be connected with the drive shaft of a prime mover. The output side of one of the two clutches is non-rotatably connected with a hollow shaft which supports one shaft connected with the output side of the other clutch. Besides gear wheels for the second and the fourth gear are fastened on the hollow shaft, the same as gear wheels for the first gear, the fifth gear, the third gear and the reverse gear are fastened on the free area of the other shaft. These fixed gears of one of each reduction step mesh with coordinated idler gears which are situated on a paraxial countershaft and can be connected with the shaft by means of synchronizer clutches (shifting sets). Each one of the synchronizer clutches is coordinated with two transmission gears. The gear sequence of this transmission, departing from the dual clutch is: second gear, fourth gear, first gear, fifth gear, third gear and reverse gear.
From DE 41 37 143 A1 is, in addition, known a multi-speed synchronized countershaft transmission where the positions of the two gears are each coordinated with one of several shifting sets. The shifting sets are, as a rule, comprised of sliding sleeves which are axially, displaceably, but non-rotatably situated on a transmission shaft and which, during a shifting operation, interacting with synchronizer rings located adjacent to the sleeves, decelerate idler gear wheels and can non-rotatably connect them with the transmission shaft.
In this known transmission, the two gears (first gear and third gear or second gear and fourth gear) coordinated with one shifting set are two non-successive transmission gears. This transmission design has the advantage that thereby is created a transmission shifting system with which an overlapping shift actuation and therewith reduced shifting times are possible but, nevertheless, such a transmission cannot be shifted via a shifting device having one H-shifting gate since, with such a transmission, only immediately consecutive transmission gears can usually be engaged in the same shifting gate.
To overcome the problem, the not pre-published DE 102 53 259.1 has proposed a universally shiftable dual-clutch transmission essentially consisting of one starting unit, one core transmission and one output unit, the starting unit comprising one single clutch, one dual clutch or one torque converter and the output unit containing transmission parts for a front-transverse drive, for a front-longitudinal drive, for a rear-longitudinal drive or for an all-gear drive. The core transmission is designed as countershaft transmission having available at least one input shaft, one countershaft and one transmission output not coaxially aligned with at least one transmission input shaft.
The gear sequence in the transmission is such that, departing from the clutch, there follow first the sixth gear, the second gear, the reverse gear, the seventh, the fifth, the third and the first gears. The fixed gears of the fourth, sixth, second and of the reverse gears are non-rotatably fastened on one hollow shaft connected with the output side of one of the two clutches of a dual clutch, while the fixed gears of the seventh, of the fifth, of the third and of the first gears are fastened on a shaft coaxially supported in the hollow shaft and connected with the output side of the second clutch of the dual clutch.
The two transmission input shafts are supported by means of roller bearings situated between the dual clutch and the gear wheel for the first gear, at the end of the hollow shaft between the gear wheels for the reverse gear and the seventh gear and, on the free end of the second transmission input shaft, supported in the hollow shaft. The same is provided for the countershaft. In addition, it is to be stated that the output of the countershaft is tied to the beginning or end thereof according to drive technology.
Against this background, the problem on which the invention is based is to introduce a transmission structure which can be used for automatic dual-clutch transmissions, automated countershaft transmissions with one clutch and simply, manually shiftable countershaft transmissions and, which compared to the prior art, has a simple constructional design, short length and an improvement relative to the support of the transmission shafts.